This is probably an easy question for some, but I would really appreciate some insight. With an earlier version of Oxygen, I remember being able to use the external validation function on a schema in order to validate an ISO Schematron. Are you still able to do this? It seems like I can only use the external validation tool with an xml file and not a schema. Are you now required to embed your schematron into a schema document? I would like to keep them separate, but I'm having trouble figuring out how to test.

A Schematron schema, that is a file with the .sch extension is opened by default in a Schematron editor panel. In this editor you don't need to set any schema for validating the Schematron schema because the action Validate Document does that. In case of the Schematron editor the action Validate Document checks the validity of the edited file as a Schematron schema.